Woven fabrics may be used during surgery to repair or replace various damaged or diseased lumens within the human body. A typical surgical procedure is vascular surgery in which a woven tubular prosthesis is used to repair a blood vessel. Grafts in which the lumen has a constant diameter have been used successfully, however, problems have persisted in procedures in which the lumen diameter changes. In one application, the lumen tapers from a first diameter to a smaller second diameter. In another application, the lumen branches. In a branched application, the implant may be formed by suturing together a number of separate lumens. Such a procedure is time consuming. Other known procedures of weaving bifurcated implants result in unacceptable seams and/or transitions.
Additionally, it is desirable to maintain a substantially consistent porosity in a woven implant. In particular, changes in porosity can lead to unacceptable voids or gaps in an implant that would require suturing during the procedure to eliminate potential leakage through the wall of the implant.